Moisander P H, McClinton E, Paerl H W
University of North Carolina at Chapel Hill, Institute of Marine Sciences, 3431 Arendell Street, Morehead City, NC 28557, USA.
Microb Ecol. 2002 May;43(4):432-442. doi: 10.1007/s00248-001-1044-2. Epub 2002 Apr 8.
Salinity has been suggested as being a controlling factor for blooms of N2-fixing cyanobacteria in estuaries. We tested the effect of salinity on the growth, N2 fixation, and photosynthetic activities of estuarine and freshwater isolates of heterocystous bloom-forming cyanobacteria. Anabaena aphanizomenoides and Anabaenopsis sp. were isolated from the Neuse River Estuary, North Carolina, and Cylindrospermopsis raciborskii from Lakes Dora and Griffin, central Florida. Salinity tolerance of these cyanobacteria was compared with that of two Nodularia strains from the Baltic Sea. We measured growth rates, N2 fixation (nitrogenase activity), and CO2 fixation at salinities between 0 and 20 g L(-1) NaCl. We also examined photosynthesis-irradiance relation-ships in response to salinity. Anabaenopsis maintained similar growth rates in the full range of salinities from 2 to 20 g L(-1) NaCl. Anabaena grew at up to 15 g L-', but the maximum salinity 20 g L(-1) NaCl was inhibitory. The upper limit for salinity tolerance of Cylindrospermopsis was 4 g L(-1) NaCl. Nodularia spp. maintained similar growth rates in the full range of salinities from 0 to 20 g L(-1) . Between 0 and 10 g L(-1), the growth rate of Nodularia spumigena was slower than that of the Neuse Estuary strains. In most strains, the sensitivity of nitrogenase activity and CO2 fixation to salinity appeared similar. Anabaenopsis, Anabaena, and the two Nodularia strains rapidly responded to NaCl by increasing their maximum photosynthetic rates (Pmn). Overall, both Neuse River Estuary and Baltic Sea strains showed an ability to acclimate to salt stress over short-(24 h) and long-term (several days to weeks) exposures. The study suggested that direct effect of salinity (as NaCl in these experiments) on cyanobacterial physiology does not alone explain the low frequency and magnitude of blooms of N2-fixing cyanobacteria in estuaries.
盐度被认为是河口固氮蓝藻水华的一个控制因素。我们测试了盐度对河口和淡水异形胞形成水华的蓝藻分离株生长、固氮及光合活性的影响。阿氏鱼腥藻和拟鱼腥藻从北卡罗来纳州纽斯河河口分离得到，莱氏柱孢藻从佛罗里达州中部的多拉湖和格里芬湖分离得到。将这些蓝藻的耐盐性与来自波罗的海的两种结节藻菌株进行了比较。我们在0至20 g L(-1) NaCl盐度下测量了生长速率、固氮（固氮酶活性）和二氧化碳固定情况。我们还研究了光合作用-光强关系对盐度的响应。拟鱼腥藻在2至20 g L(-1) NaCl的整个盐度范围内保持相似的生长速率。鱼腥藻在高达15 g L(-1)时生长，但20 g L(-1) NaCl的最大盐度具有抑制作用。莱氏柱孢藻的耐盐上限为4 g L(-1) NaCl。结节藻属在0至20 g L(-1)的整个盐度范围内保持相似的生长速率。在0至10 g L(-1)之间，泡沫节球藻的生长速率比纽斯河口菌株慢。在大多数菌株中，固氮酶活性和二氧化碳固定对盐度的敏感性似乎相似。拟鱼腥藻、鱼腥藻和两种结节藻菌株通过提高其最大光合速率（Pmn）对NaCl迅速做出反应。总体而言，纽斯河河口和波罗的海菌株在短期（24小时）和长期（数天至数周）暴露下均显示出适应盐胁迫的能力。该研究表明，盐度（在这些实验中为NaCl）对蓝藻生理的直接影响并不能单独解释河口固氮蓝藻水华的低频率和规模。
